The world's largest wildlife survey, dubbed the "Big Garden birdwatch" is being launched by the UK's Royal Society for the Protection of Birds.
The charity hopes that around half a million people will record the abundance of different bird species visiting their gardens and open spaces.
By asking members of the public to spend one hour this weekend spotting birds, the charity can identify those species in most need of help.
The survey is now in its 31st year.
This year the survey, which starts on Saturday, 30 January, will be particularly useful in helping conservationists understand the impact of the "big freeze" on bird populations, and whether some species have suffered or changed their behaviour more than others.
"We can expect to see some more unusual visitors to gardens, particularly redwings, fieldfares and tree sparrows that are struggling to find food elsewhere," says Dr Mark Avery, the RSPB's Director of Conservation.
The extraordinarily harsh recent weather is particularly bad for birds with small bodies like robins, long tailed-tits and wrens.
"It's unlikely the long tailed tit, which famously flew into tenth place in 2009, will remain in the top ten this year," says Dr Avery.
"Sadly, we may even see the nation's favourite garden bird, the robin, also fall out of the top ten in 2010. If this is the case, it'll be the first time the robin hasn't featured in the top ten since the start of the survey."
To take part in the survey, the RSPB asks people to download a form from its website, and use it to record the highest number of every bird species seen at any one time.
This data is then collated across the country to give an overall indication of how populations of different species are faring.
For example, the survey helped reveal that starling numbers in gardens have fallen by 77% between 1979 and 2009.
Similarly, house sparrow numbers have fallen by 64% over the past 30 years.
However, blue and great tits have endured, making regular appearances each year in the top 15 most abundant species.
Last year, 551,881 participants helped record over 8.5 million birds across nearly 280,000 gardens.
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